1. Field of the Invention
The present invention relates generally to an apparatus for heating and mixing asphalt-aggregate composition and, more particularly, to an assembly for use with such an apparatus to introduce reclaimed asphalt pavement particles into the apparatus for heating and mixing with virgin aggregate particles.
2. Discussion of the Prior Art
It is known to carry out hot-mix recycling of reclaimed asphalt pavement by either a batch or drum-mix recycling process. In drum-mix plants, reclaimed asphalt pavement (RAP) is introduced into a rotatable drum downstream of a burner flame and mixes with super-heated new aggregate particles which enter the drum adjacent the flame at the inlet of the drum. In this manner, it is possible to distance the RAP from the flame in order to reduce "blue smoke", an environmental problem arising from exposing the RAP to relatively high temperatures, e.g. greater than about 275 degrees Fahrenheit.
Typically, a dense veil of virgin aggregate particles are showered in front of the entering RAP particles in order to further shield the RAP particles from exposure to the flame. In other known constructions, mechanical shields are provided to carry out a similar function with the goal of reducing "blue smoke" to an acceptable level.
Certain drawbacks exist with each of these known constructions. For example, if the aggregate particles are used as a shield for the RAP particles, then special flighting is required within the drum or additional inlet openings are required to direct virgin material into the path of the flame to prevent exposure of the RAP particles to the flame. Further, where mechanical shields are used, supplementary hardware is required in addition to the hardware used to introduce the RAP particles into the drum in order to convert an existing drum plant into a plant capable of recycling RAP. Thus, such constructions are expensive to install and tend to render the plant less efficient than would be the case if the heat from the flame were more fully utilized in the heating process.